This invention relates to a two-stroke engine and more particularly to an improved combustion chamber and porting configuration for such an engine.
The advantages of two-stroke crankcase compression internal combustion engines are well known. Such engines have particular utility because of their extremely simple design and also because of their relatively high specific output for the size of the displacement of the engine. However, the very features which make two-cycle engines desirable also give rise to certain deficiencies. That is, because of the two-stroke cycle of operation, the fresh intake charge is being drawn into the combustion chamber at the same time the previously burnt charge is being exhausted from it. Therefore, there is a danger that either the chamber will not be fully purged of the previous combustion products, or alternatively, a portion of the incoming fresh fuel/air mixture will pass out of the exhaust port and be lost without ever having been burned. In addition, it is important that the combustion chamber configuration and spark plug location be chosen so that the entire charge within the combustion chamber is burned before it is exhausted from the exhaust port.
In the co-pending application entitled "Combustion Chamber For Spark-Ignited Engine", Ser. No. 936,337, filed Dec. 1, 1986 in the name of Kimihiro Nonaka and assigned to the assignee of this application, there is disclosed a combustion chamber configuration for a two-cycle engine that is particularly efficient in insuring that the entire charge in the chamber is burned. That patent application also shows an engine embodying a type of scavenging which is found to be particularly effective and which is called the loop or Schnule scavenging. With this type of scavenging, the exhaust port or intake ports are on opposite sides of the combustion chamber and the flow through the combustion chamber follows a loop pattern looking at the chamber in vertical cross section. However, it has been found that the type of scavenging system employed in that engine can be improved so as to insure that none of the fresh air/fuel mixture will flow out of the exhaust port while at the same time insuring that all of the burned fuel/air mixture from the previous cycle has been exhausted.
It is, therefore, a principal object of this invention to provide an improved combustion chamber and porting arrangement for a two-cycle engine.
It is a further object of this invention to provide an improved combustion chamber and loop scavenging system for a two-cycle, internal combustion engine.